In vehicles and the densely populated areas of urban road, for example, bicycles, electric bicycles, tricycles or a motorcycles are shuttled, which lack a highly recognizable safety indicator, at the same time, when the above vehicles are used, it is difficult for the rear vehicle to clearly understand the braking intention of the bicycle, electric bicycle, tricycle or a motorcycle in front, it is difficult to grasp the brake condition of the user immediately, which is likely to cause a rear-end collision of the rear vehicle, at the same time, in vehicles and the densely populated areas of existing urban road there are no obvious tip lights on the bicycles and electric bicycles that are riding, which is not safe enough, to this end, it is proposed that a brake warning device, which is safe and reliable, can know the intention of using the brake in real time, this is the idea of the present invention.